This study reports the findings of an investigation into the roles of English, standard written Chinese and Cantonese in the workplace in post-colonial Hong Kong. The study was motivated by the paucity of large-scale, broad-spectrum research into language use in workplace communication in Hong Kong. Previous studies, while helpful and suggestive, have tended either to focus on language use within a single profession, or are small-scale in scope. The findings of this study derive from a questionnaire survey of 3,019 subjects employed in both the public and private sectors and by Hong Kong-owned and foreign-owned organisations. Subjects mostly held junior rank within their employing organisations and were drawn from large, medium-sized and small employing concerns within the five broad professional fields of Business Services, Community and Social Services, Construction and Real Estate, Engineering, and Manufacturing. A multi-method approach to data collection was adopted to achieve triangulation: the quantitative survey data were analysed statistically and are interpreted partly by reference to qualitative data elicited from a focus group interview with participating subjects and five individual case study subjects who kept a written record of their language use over a single typical working week. Results indicate that English continues to function as the unmarked language option for internal and external written communication in both the public and private sectors of the local economy. Chinese professionals who work for foreign-owned organisations in Hong Kong make greater use of English in written communication than do their counterparts in Hong Kong-owned companies. Professionals who work for large Hong Kong concerns manifest a slightly greater need to read or write in English than those who work for small local companies. In terms of spoken communication, Cantonese emerges clearly as the unmarked language option for intra-ethnic communication in informal situations.